1. Field of the Invention
The present invention relates to a developing device for developing an electrostatic latent image, and a process cartridge including such developing device and removable with respect to an image forming apparatus.
2. Related Background Art
In developing devices, in order to feed out developer from a container containing the developer and convey the developer to a developing station where an electrostatic latent image is developed, a rotatable developer bearing member such as a developing roller or developing sleeve has been used. The rotatable developer bearing member returns the developer which was not adhered to the electrostatic latent image to the container.
In many conventional developing devices, a flexible sheet member made of polyethylene terephthalete is arranged at a return opening of the container, so that the developer returned from the developing station by the developer bearing member is permitted to pass through the return opening and enter into the container, but the developer in the container is prevented from leaking through the return opening toward a direction opposite to a rotational direction of the developer bearing member.
The flexible sheet member is urged against the developer bearing member along a longitudinal direction thereof. Further, the flexible sheet member is secured to a fixing surface of the container at a position upstream of an urged portion between the developer bearing member and the sheet member in the rotational direction of the developer bearing member.
By the way, it is difficult to urge the flexible sheet member against the developer bearing member with high accuracy, and the urging condition between the sheet member and the developer bearing member varies as the developing device is used for a long time. If the urging condition between the sheet member and the developer bearing member is improper, the developer in the container will leak and/or the developer returned from the developing station will be prevented from passing through the return opening, thereby causing the scattering of the developer.
On the other hand, in some developing devices, an elastic regulating member made of urethane rubber and the like is urged against the developer bearing member to regulate a thickness of a layer of the developer conveyed to the developing station by the developer bearing member. Further, generally, side seal members made of moltprene, felt or the like are urged against both longitudinal end portions of the developer bearing member along the rotational direction of the developer bearing member so as to prevent the developer from leaking through such end portions.
However, it is not preferable that longitudinal ends of the elastic regulating member are abutted against the side seal members, because such abutment causes elastic deformation of a portion of the elastic regulating member, thus making the urging force between the elastic regulating member and the developer bearing member uneven or non-uniform to lead in the uneven thickness of the developer layer.
Accordingly, it is necessary to provide small clearances or gaps between the ends of the elastic regulating member and the side seal members. In this case, the developer in the container will leak through such gaps. If the developer leaked through the gaps is not positively collected or returned to the container, the scattering of the developer will occur.